Play testing game system

I have trouble finding players in my area to beta-test my rules. Can I conduct a playtest via email instead? I have not fleshed out a world theme yet, but I do have a great idea that fits my rules. What I can do instead is use other world systems like ShadowRun, EarthDawn, and DnD.

Should I seek Beta Testers for a PBeM system and should I specify which world they will be playing in?